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I have a simple problem which (to me) seems to be difficult to solve in ArcGIS. The map I plot is a GeoTIFF with emission data. I use a default algorithmic color ramp (rainbow) to do so. Now I would like to replace the lowest value (=0.0) with white instead of blue.

The only solution I have come up with yet is to create a new Mulltipart color ramp with the first part being preset and the second algorithmic. This way, the color steps in the first part are much coarser than in the second one. Is there a way to reduce the number of colors in the preset color ramp to 1?

Any help is really appreciated - thanks!

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2 Answers

up vote 4 down vote accepted

If I'm understanding your goals correctly, here's how I would approach the problem. Storytelling by screenshots:

1) Go to the properties > Symbology tab for your layer.

2a) In the left-most props window, I chose a color ramp. Notice I inverted it.

2b) Next, I right-click the ramp and select Properties.

3) In the middle properties window, select the ramp you want to modify and choose Properties.

4) In the right-most props window, in my case, I changed Color 2 from dark blue to white, then saved my way out.

Caveat (see 2b): When you invert the color ramp, you won't see the result of this in the horizontal ramp, but you will in the vertical ramp to the left. Don't let this be confusing.

enter image description here

Finally, this is the result I got. It seems to me you're wanting something about like this, yes?

enter image description here

PS. I used a DEM to demonstrate the color ramp modifications because I thought that was my most comparable dataset. So in this case, highest elevations in Jamaica are appearing as red, while the lowest elevations are light-blue/white.

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OK, now I get it. The thing I failed to understand was that you can create a ramp from white to blue... Thanks a lot!! –  Daniel Oderbolz Dec 14 '11 at 13:42
    
The only problem with this is that the range of values covered by blue increases compared to for example red. Of course I can add more ramps to the multipart ramp, but the problem will not go away. If one could control the number of colors in a preset ramp, that would solve it, but I think it cannot be done... –  Daniel Oderbolz Dec 14 '11 at 14:04
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I have found another solution that does not involve editing the color ramps. ArcGIS allows to color a given value (the background color) in its own color - this is exactly what I wanted: Another solution: Use the background color

So I will stick with a default colorscale and just color 0 white.

Thanks anyways, elrobis!

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+1 And it was right there on that first props screen all along. Nice catch. :) –  elrobis Dec 14 '11 at 15:02
    
You might be able to unaccept my answer and accept this one in its place. –  elrobis Dec 14 '11 at 15:05
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